I just found this article in the Medical Journal of Australia (MJA) while waiting for midnight ... Happy New Year!

Glucocorticoid‐induced adrenal suppression: physiological basis and strategies for glucocorticoid weaning.
https://www.mja.com.au/journal/2023/219/10/glucocorticoid-induced-adrenal-suppression-physiological-basis-and-strategies
What do you think? I remembered you were from Australia.

As for splitting your prednisone dose, I can confirm it worked for me. I had the advantage of being able to see the inflammation inside my eye because of uveitis.
https://www.aao.org/eye-health/diseases/what-is-uveitis
It was strange how I could see some improvement by the evening when I took my entire prednisone dose in the morning. Inevitably the inflammation got worse overnight. Sometimes the inflammation that occurred overnight was much worse than the previous morning and I needed to increase my prednisone dose.

The opposite happened when I spit my dose. The improvement that happened by evening was sustained overnight when I took a small amount of prednisone in the evening. By the time I woke up the next morning, the inflammation was better than it was the evening before. My eye inflammation was markedly improved compared to the morning before.

This is mostly anecdotal evidence compared to empirical evidence. My ophthalmologist agreed and said whatever I was doing -- he could see the difference too.

I did the same for PMR and it worked at higher doses but not so much at lower doses. I was on prednisone for a long time for PMR. I was tired of waking up every morning in pain and splitting my dose spared me most of the morning pain.

With uveitis, I could go from 60 mg to zero in less than a month. I didn't need to take prednisone too long to achieve remission of uveitis.

Splitting your dose for PMR/GCA may only work at higher doses of prednisone. When I got down to the physiological dose of prednisone (approx. 7 mg) nothing worked well. I just needed a different medication that didn't suppress my adrenal function and then I was able to taper off prednisone rather quickly after that.